This invention relates to a disposable plate electrode with biological active film and manufacture method thereof, particularly to a manufacture method that can produce plate electrode speedily and to a disposable plate electrode which is used to cooperate with a biosensor for composition analysis and concentration measurement of a test sample in accordance with the electrical output resulted from biochemical reaction.
The biochemistry analyzer is usually classified into three categories, namely, the wet type analyzer, the dry type analyzer, and the biosensor. Application of a conventional wet type biochemistry analyzer is to mix a test sample with reagent (a chromatic agent is commonly contained) for chemical reaction, then an optical reading device, such as a colorimeter or a spectrophotometer, is used to read color change before and after the reaction. This test way is weak at: a pre-treatment required for the test sample; difficulties in dosing and keeping a reagent valid for a long period; expensive instruments; and unfeasibility for non-professional operation, so that it fits a hospital or an examining center for mass sample analyses better than few quantity or emergency tests.
As to application of the dry type biochemistry analyzer, a test strip is coated on its surface with a chemical reagent, such as an enzyme, or antibody, etc to contact directly and react with the test sample for analysis. Though this test way can save dosing and adding process of the reagent, color of the test strip may be changed due to oxidation to affect color judgment before and after reaction.
The biosensor is composed of a biological element, a thin film element, and a sensor, wherein the biological element is made from biological material with cognizable specialties, such as microbe, cell, tissue, enzyme, antigen, and antibody, etc; the thin film element is usually made from polymeric material and used to fix the biological element and sieve out interference substance; and, the sensor may comprise electrodes, ion selective field effect transistors, thermistors, piezoelectric devices, optical fiber, photoelectric tubes, and sound wave counters, etc., and wherein the hydrogen peroxide electrode is the one most widely used.
Take the biosensor for analyzing blood glucose for instance, glucose is oxidized and fixed on a thin film, which is clad tightly on surface of a pillar hydrogen peroxide electrode, then a polarized potential is applied to the platinum anode and the silver/silver chloride cathode, the hydrogen peroxide produced by oxidation of the glucose will continue to be oxidized to water near surface of the anode, and meanwhile, release electrons. The glucose concentration of the test sample may be calculated according to the released amount of electrons.
The aforesaid pillar electrodes shall require constant refreshment including polishing, film clothing, cleaning, and recalibrating, etc, which may incur cross pollution owing to carelessness in addition to inconvenient implementation, not to mention the high production cost. For eliminating above defects, the U.S. Pat. No. 4,545,382 of Genetics International in UK has disclosed a blood glucose meter xe2x80x9cExactechxe2x80x9d which is the first commercially realized example of a plate electrode in this field.
In U.S. Pat. No. 5,120,420xe2x80x94Biosensor and process for preparation thereof, another disclosed biological detecting plate electrode comprises an electrode portion, an insulation layer, a reaction layer, and a test sample bearing space on the reaction layer, wherein a sample inlet port and an gas exhaust port are provided to the bearing space. The reaction layer is formed by coating subsequently CMC (Carboxymethyl Cellulose) water solution on the electrode substrate to form a CMC layer, water solution of GOD (Glucose Oxidase), and then a suspending liquid containing conductive mediator to form a biochemistry reaction portion. Finally, a resin plate and a top plate are used to cover on the substrate to form the sample bearing space and complete thereby the biological detecting plate electrode.
The biochemistry reaction portion of the aforesaid U.S. Pat. No. 5,120,420 is formed in 3 steps, namely:
1. The CMC layer used to improve hydrophobicity of the carbon electrodes.
2. The GOD layer.
3. The conductive mediator layer.
Each step requires drying before completed.
This invention is proposed to provide a new fabrication process for plate electrode, which is provide at least with an electrode portion used to transmit electrical effect produced from biological reaction; and a biological active layer used to conduct a chemical or biochemical reaction with a test sample. The biological active layer comprises at least 3 portions: an absorptive carrier layer, an enzyme, and a conductive mediator. The carrier is printed on surface of the electrode portion with screen-printing technique and used to suck and sustain the biological active substance (such as enzyme) and the conductive mediator. Also, the carrier can turn the electrode portion from hydrophobic into hydrophilic, and moreover, protect the biological active substance against impairment in relatively high temperature drying process to make a speedy production of the plate electrode become possible.
Another object of this invention is to provide a simplified process for production of the plate electrode, wherein the carrier layer is printed on an insulating substrate of the plate electrode with screen-printing technique.